Relatively few human studies have been carried out into the effects of smoking cannabis during pregnancy – although rat studies have suggested the drug can cause brain damage.

America’s National Institute on Drug Abuse says that more research is needed to separate marijuana use from other factors, but says, ‘Human studies have shown that some babies born to women who used marijuana during their pregnancies respond differently to visual stimuli, tremble more, and have a high-pitched cry, which could indicate problems with neurological development.’